Abstract 2212: Computational Model of Exercise Effects on Fontan Hemodynamics Demonstrates Favorable Energetics In Extracardiac Fontans When Compared to Lateral Tunnel
Background: Previous computational experiments using anatomically correct Fontan geometries have suggested that extracardiac Fontans (EC) have lower power loss compared to lateral tunnel intracardiac (IC) Fontans. Differences in exercise performance may also be important in the long term morbidity of Fontan patients. We have previously developed a computational model for studying exercise conditions.
Hypothesis: It is our hypothesis that the EC total cavopulmonary connection (TCPC) is more hemodynamically favorable and demonstrates significantly lower resistance at exercise.
Methods: We performed steady flow CFD simulations on 3-D anatomical reconstructions of TCPC from 9 Fontan patients using cardiac magnetic resonance imaging (CMR) data, 5 with EC and 4 with IC. Caval flows were determined using CMR velocimetry and outlet pulmonary artery pressures tuned to obtain flow splits corresponding to equal vascular lung resistance (EVLR) of 2 Woods units for each lung. Simulated exercise conditions of twice (2x) and three times (3x) baseline MRI flow were performed by increasing IVC flow. Power loss calculations using control volume analysis were performed for each TCPC and each flow condition studied. Power losses were normalized to calculate a resistance index and the two groups compared using the Student t-test for independent groups.
Results: Resistance index was significantly greater in IC compared to EC Fontans for all three flow conditions. This difference was magnified at exercise flow conditions. At baseline flow, EC TCPC resistance index was 0.14 compared to 0.49 Woods units for IC (p = 0.001). This rose to 0.29 and 0.81 for EC and IC TCPC respectively for the 2x exercise condition (p = 0.002), and to 0.44 and 1.2 for the 3x condition (p = 0.008). There was no significant difference in cardiac output between EC and IC pts, but the EC pts were significantly younger.
Conclusions: CFD modeling of 3-D anatomical reconstructions demonstrates significant differences in power loss between EC and IC TCPC which are magnified at exercise conditions. The differences are hemodynamically significant, as high as 0.76 Woods units at the highest exercise flow condition, and are thus likely important in the long-term survival and quality of life of patients with TCPC.